System for controlling the release of fuel vapors from a vehicle fuel tank

ABSTRACT

A system and method for controlling the release of fuel vapors and liquid fuel from a vehicle fuel tank is provided. The system includes a vent path leading from the dome of the fuel tank to a vapor capture device such that when the fuel tank cap is in place the vent path is opened when the pressure in the dome exceeds a predetermined value, when the cap is removed the vent path is opened irrespective of the pressure in the dome, and upon insertion of the fuel nozzle into the filler pipe the vent path is closed.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional application of a co-pending applicationSer. No. 253,855, filed Oct. 5, 1988, now U.S. Pat. No. 4,874,020, whichis a continuation-in-part application of copending application Ser. No.031,030 filed Mar. 26, 1987, now U.S. Pat. No. 4,887,652.

BACKGROUND OF THE INVENTION

This invention relates to a system for controlling the release of fuelvapors into the atmosphere from the fuel filler pipe of a vehicle's fueltank.

As currently designed, vehicle fuel tanks normally operate under apositive pressure. Accordingly, when the filler cap for such a tank isremoved, fuel vapors are released into the atmosphere. Similarly, as thetank is filled with fuel, fuel vapors in the tank are forced out of thetank into the atmosphere by the incoming fuel. The release of fuelvapors into the atmosphere under these conditions is undesirable forboth environmental and health reasons.

The present invention is directed to controlling the release of fuelvapors into the atmosphere under the foregoing conditions. Specifically,rather than allowing the vapors to escape, the invention routes them toa vehicle-mounted, vapor capture device, such as, a charcoal canister,from which the vapors can be later removed and safely burned in thevehicle's engine.

In addition to controlling vapor escape, the invention also preventsliquid fuel from flowing into the vapor capture device during filling ofthe fuel tank. Moreover, the invention provides automatic relief forover pressure conditions within the vehicle's fuel tank, is easy toconstruct, reliable, crash-worthy, and can be readily installed in placeof conventional filler pipe assemblies.

In addition to the foregoing, an important application of the inventionis to the problem of expulsion of liquid fuel from a vehicle fuel tankafter removal of the filler cap. Such expulsion is known to occur forcertain vehicles when fuels having an elevated volatility are used orwhen the vehicle is operated under conditions which result insignificant heating of the liquid fuel in the fuel tank. For example,fuel expulsion has been observed for ambulances operated during hotweather and for vehicles in which parts of the exhaust system lieparticularly close to the fuel tank.

The expulsion is caused by rapid vaporization of hot fuel in the tankafter the pressure in the tank has been released through removal of thefiller cap. Depending on the design of the tank and the tank's fillerpipe, the amount of fuel left in the tank, and the orientation of thevehicle, such vaporization can eJect significant amounts of fuel out ofthe tank and onto the person who removed the cap. This is obviously ahighly dangerous and potentially lethal event and in practice has beenfound to be an extremely difficult problem to solve for those vehicleswhich exhibit the problem.

As discussed below, the present invention solves the problem while atthe same time providing reliable venting of the fuel tank during normaloperation and reliable shut-off of service station fuel pumps duringfilling of the fuel tank.

SUMMARY OF THE INVENTION

To achieve the foregoing and other goals, the invention provides a fuelfiller pipe assembly comprising an outer tube whose lower end isconnected to the vehicle's fuel tank and whose upper end is attached,for example, to the sheet metal of the vehicle. The tube has a mouth atits upper end for receiving fuel, to which a cap is attached during useto seal closed the mouth. Preferably, the cap has a male screw threadwhich mates with a corresponding female screw thread formed in the mouthof tube.

The inside of the outer tube includes a partition which divides theinterior of the tube into two conduits--a first conduit for carryingfuel from the mouth to the fuel tank and a second conduit, isolated fromthe mouth, for carrying fuel vapors out of the fuel tank to the vaporcapture device. In certain preferred embodiments of the invention, thepartition is in the form of an inner tube disposed within the outertube. For this configuration, the bore of the inner tube carries fuelfrom the mouth to the fuel tank, and the space between the inner andouter tubes carries fuel vapors to the vapor capture device.

Attached to the second conduit is a third conduit for connecting thesecond conduit to the vapor capture device. Passage of fuel vaporsthrough the third conduit is controlled by a valve assembly. The stateof this assembly, i.e., whether it is open or closed, is controlled bythe attachment and detachment of the filler cap to the outer tube.Specifically, attachment of the cap causes the valve assembly to closeso as to seal the fuel tank, while detachment causes the assembly toopen so that fuel vapors are routed from the fuel tank to the vaporcapture device.

In this way, the fuel tank can be pressurized during normal operation ofthe vehicle with the cap in place. As the cap is removed, the valveassembly opens thus venting substantially all of the pressurized fuelvapors within the tank to the vapor capture device, rather than allowingthese vapors to escape into the atmosphere. Similarly, as fuel isintroduced into the tank through the mouth of the tube, substantiallyall of the fuel vapors which are displaced by the entering fuel leavethe tank through the second and third conduits and the open valveassembly, rather than through the mouth of the tube. To further ensurethat the displaced fuel vapors leave the tank though the second andthird conduits, a seal is preferably formed between the fuel fillernozzle and the first conduit.

In certain preferred embodiments of the invention, wherein a male screwthread is used on the cap and a female screw thread is formed in themouth of the outer tube, the coordination between the opening andclosing of the valve assembly and the detachment and attachment of thecap is achieved by the movement of the male screw thread within thefemale screw thread. In connection with these embodiments, it is furtherpreferred to use a valve assembly which includes a normally-closed valveconnected to a mechanical linkage which is activated by contact with themale screw thread as that thread rotates within the female screw thread.

As discussed in detail below, a preferred form of such a mechanicallinkage comprises a pivoted cam arm, a spring which urges the cam arminto contact with the normally-closed valve to open that valve, a secondpivoted cam arm which is contacted by the male screw thread, and arotatable post which connects the two cam arms so that contact of themale screw thread with the second cam arm causes that arm to rotatewhich, in turn, rotates the first cam arm, moving it away from the valveso that the valve can close. As also discussed below, it is furtherpreferred to place a vapor barrier between the cam arms so as to preventfuel vapors from reaching the mouth of the outer tube by following thepath of the mechanical linkage.

In addition to the foregoing, it is also preferred that the valveassembly include a normally-closed valve which is designed to open whenthe pressure within the fuel tank exceeds a predetermined value. In thisway, excess pressure which may develop within the tank is automaticallyvented to the vapor capture device.

In connection with other preferred embodiments, a second valve (liquiddiscrimination valve) is provided which closes the second conduit whenliquid fuel reaches a predetermined level within the second conduit.This valve prevents substantial amounts of liquid fuel from being pumpedinto the vapor capture device during filling of the fuel tank. When sucha valve is used and when a seal between the first conduit and the fuelfiller nozzle is also used, it is further preferred to provide anoverpressure or relief valve between the second conduit and the mouth ofthe outer tube so as to provide a path for fuel to leave the fuel tankif the automatic shut-off of the fuel filler pump should malfunction andnot shut off the pump once the fuel tank has been filled or if the usershould continue to pump fuel into the tank after the tank is full.

As discussed below, a preferred form for the second valve comprises aball and seat valve employing a ball having a lower density than theliquid fuel so that the ball rises into the seat and closes off thesecond conduit as the level of fuel rises in that conduit. As alsodiscussed below, in connection with this valve configuration, it is alsopreferred to baffle the second conduit so as to minimize the chance thatliquid fuel splashed up during the filling process will reach the balland close the valve before the fuel tank has been completely filled. Inaddition, it is preferred to place a ball, e.g., a metal ball, having ahigher density than the liquid fuel below the ball with the lowerdensity so that if the vehicle should roll over, the second valve willautomatically close by means of the higher density ball forcing thelower density ball into the valve seat.

An important feature of the invention is the fact that in terms of itsrelationship to the vehicle, the assembly of the invention has basicallythe same structure as conventional filler pipes. Thus, as with aconventional filler pipe, there is only one connection between theassembly and the vehicle's fuel tank. Similarly, the mouth of theassembly is mounted to the vehicle in the same manner as conventionalfiller pipes. Accordingly, the assembly of the invention can be used inplace of conventional filler pipes with a minimum of changes to themanufacturing process. Also, because of the similar structure andattachment points, crashworthiness of the overall fuel supply system isnot compromised by the substitution of the assembly of the invention fora conventional filler pipe.

As discussed above, an important application of the invention is to theproblem of fuel expulsion from the filler pipe of a vehicle's fuel tankupon removal of the filler cap. If the temperature and volatility of thefuel in the tank are high enough, the reduction in tank pressure whichoccurs when the filler cap is removed can result in rapid vaporization("boiling") of the heated fuel. Depending on a variety of variables,including the amount of fuel left in the tank, the orientation of thevehicle, and the design of the tank and the filler pipe, this rapidvaporization, in turn, can cause fuel to be expelled from the fillerpipe.

The filler pipe assembly of the invention, by releasing the pressure inthe tank as the filler cap is removed from the filler pipe,significantly reduces the chances of expulsion since it allows time forthe fuel to cool through vaporization before the cap is completelyseparated from the filler pipe. The fuel vapors produced during thecooling process are routed to the vapor capture device by thecap-controlled valve assembly and thus do not escape into theenvironment.

For some vehicles, however, even this cooling is not sufficient toguarantee no expulsion under all operating conditions. To provide thislevel of assurance, the filler pipe assembly is combined with thefollowing components which together essentially completely eliminate theproblem of expulsion: (1) a first, normally-closed, flapper door and aflapper-door/fuel-nozzle seal, both of which are located in the regionof the the mouth of the filler pipe assembly, above the level at whichfuel vapors pass into the cap-controlled valve assembly: (2) a second,normally-closed, flapper door and a flapper-door seal, both of which arelocated below the level at which fuel vapors pass into thecap-controlled valve assembly: and (3) a vent conduit which connects thefuel tank to the filler pipe assembly at a level between the first andsecond flapper doors.

The first flapper door is spring loaded against theflapper-door/fuel-nozzle seal so as to seal closed the mouth of thefiller pipe. This door/seal combination provides the first line ofdefense against the expulsion of liquid fuel from the mouth.Specifically, the door is closed against the seal as the cap isseparated from the filler pipe assembly, and thus even if the fuel inthe tank should boil violently, no fuel can escape past the door intothe filler pipe's mouth.

The flapper-door/fuel-nozzle seal is located above the first flapperdoor. As a service station fuel nozzle is inserted into the filler pipeassembly during refueling, this seal engages the outer surface of thenozzle. As the nozzle is inserted further into the assembly, it contactsand opens the first flapper door. Because the nozzle and the seal havealready mated at this point, expulsion continues to be prevented eventhough the flapper door has opened.

The second flapper door is located below the first flapper door andbelow the cap-controlled valve assembly. This door is spring loadedagainst the flapper-door seal so as to seal closed the conduit whichcarries fuel from the mouth of the filler pipe assembly to the fueltank. The door thereby isolates the cap-controlled valve assembly fromthe fuel tank. As a result of this isolation, liquid fuel is preventedfrom reaching the valve assembly (as well as the mouth of the fillerpipe assembly) both during normal operation of the vehicle and duringtimes when the filler cap has been removed, but refueling has not yetbegun.

It is important to prevent liquid fuel from reaching the valve assemblyduring these times since, as discussed below, it is during these timesthat the valve assembly functions as part of the vent path for fuelvapors in the fuel tank. If significant amounts of liquid fuel were toreach the valve assembly and if the assembly included a liquiddiscrimination valve, as is preferred, the valve assembly would close,thus preventing further venting of the fuel tank.

During refueling, the service station nozzle contacts the second flapperdoor and pushes it open. In contrast to the flapper-door/fuel-nozzleseal used with first flapper door, the flapper-door seal used with thesecond flapper door does not form a seal with the fuel nozzle. This sealis not formed so that fuel vapors displaced from the fuel tank by theincoming fuel can pass around the nozzle, through the second flapperdoor, and through the cap-controlled valve assembly to the vapor capturedevice.

The vent conduit connects the uppermost portion or portions of the fueltank to the filler pipe assembly. This conduit carries fuel vapors fromthe tank to the cap-controlled valve assembly during (1) normaloperation of the vehicle when the filler cap is on, and (2) when thefiller cap has been removed, but refueling has not yet begun.

As discussed above, the cap-controlled valve assembly preferablyincludes a normally-closed valve which opens at a predeterminedpressure. During normal operation, with the filler cap in place, thisvalve is closed. The vent conduit connects the main body of the fueltank to this normally-closed valve. When the pressure in the fuel tankexceeds the predetermined pressure, the valve opens and the fuel vaporsin the tank flow through the vent conduit to the vapor capture deviceuntil the pressure in the tank is reduced below the predeterminedpressure, whereupon the valve closes.

The use of a pressure-controlled valve to vent the fuel tank is animportant advantage of the invention since it limits the amount of fuelvapors generated in the tank, that is, since the fuel in the tank isheld at a pressure above atmospheric pressure, it vaporizes less. This,in turn, reduces the amount of fuel vapors transferred to the vaporcapture device. This reduction, in turn, makes it easier to purge thevapor capture device to the vehicle's engine without degrading engineperformance through an overly rich fuel/air mixture. Thus, by limitingthe amount of fuel vapors formed in the fuel tank, the invention is ableto achieve an overall improvement in the functioning of the vehicle'sfuel vapor control system.

In addition to carrying fuel vapors during normal operation, the ventconduit also carries vapors when the filler cap has been removed. Underthese conditions, the pressure in the fuel tank is reduced since thecap-controlled valve assembly is open. As discussed above, thisreduction in pressure can result in rapid vaporization of liquid fuel inthe tank and thus the generation of large amounts of fuel vapor.Accordingly, it is important to size the vent conduit (and thecap-controlled valve assembly) to carry substantial amounts of vapor.

Even when so sized, some back pressure due to resistance to flow in theconduit and the valve assembly can exist in the fuel tank when fueltemperatures and/or fuel volatility are high. Depending on the amount offuel in the tank, the orientation of the vehicle, and the design of thefuel tank and filler pipe, this back pressure can cause liquid fuel tomove into the filler pipe assembly. It is for this reason that thesecond flapper door and its seal are necessary so as to prevent suchliquid fuel from reaching the liquid discrimination valve and shuttingoff the vent path.

During refueling, the vent conduit needs to be closed so that liquidfuel will be driven onto the fuel filler nozzle's aspirator to shut offthe service station fuel pump. Specifically, venting of the upperportion or portions of the fuel tank is stopped during refueling so thatliquid fuel will be driven up the fuel carrying conduit and/or aseparate shut-off conduit, if used, when those conduits become coveredwith fuel. In this way, normal fill levels to the tops of the fuelcarrying conduit and/or the shut-off conduit are achieved. Such levelspreserve a space at the top of the fuel tank for expansion of the fuel.

The desired closing of the vent conduit during refueling can be achievedmost conveniently by means of the first flapper door. Specifically, inaccordance with this approach, the portion of the vent conduit whichengages the filler pipe assembly is equipped with a seal which engagesthe bottom or back side of the flapper door as that door is pushed openby the fuel nozzle. The vent conduit is thus automatically closed whenthe fuel nozzle is inserted into the filler pipe assembly at thebeginning of refueling. Other approaches, of course, can be used ifdesired.

The operation of the flapper doors, seals, vent conduit, andcap-operated valve assembly for various tank configurations is describedin detail below in connection with the description of the preferredembodiments of the invention.

The accompanying drawings, which are incorporated in and constitute partof the specification, illustrate the preferred embodiments of theinvention, and together with the description, serve to further explainthe principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a fuel filler pipe assembly constructedin accordance with the present invention.

FIG. 2 is an exploded view of the assembly of FIG. 1.

FIG. 3 is a top view of the assembly of FIG. 1 with the fuel filler capremoved.

FIG. 4 is a side view of the assembly with the cover plate for thehousing portion of the assembly removed.

FIG. 5 is a cross-sectional view along lines 5--5 in FIG. 3. FIG. 5 alsoillustrates the mating of the fuel tank's filler cap with the fuelfiller pipe assembly.

FIG. 6 is a cross-sectional view along lines 6--6 in FIG. 4.

FIG. 7 is a cross-sectional view along lines 7--7 in FIG. 4.

FIGS. 8-11 illustrate the coordination between the opening and closingof the assembly's vapor control valve and the detachment and attachmentof the fuel filler cap to the assembly. FIGS. 8 and 9 arecross-sectional views along lines 8--8 in FIG. 4. FIGS. 10 and 11 arecross-sectional views along lines 10--10 in FIG. 4.

FIG. 12 is a cross-sectional view along lines 6--6 in FIG. 4illustrating the orientation of the filler pipe assembly when mounted toa vehicle.

FIG. 13 is a perspective view of a baffle assembly for use with thepresent invention.

FIG. 14 is a perspective view, partially in section, illustrating thefuel filler pipe assembly with the baffle assembly of FIG. 13 in place.

FIG. 15 is a cross-sectional view along lines 15--15 in FIG. 13.

FIGS. 16-23 illustrate the application of the present invention to theproblem of expulsion of fuel from a vehicle fuel tank for three types offuel tanks.

In FIGS. 16-18, the fuel tank has a single dome and a conduit separatefrom the main fuel-carrying conduit for establishing the tank's fillline, i.e., for wetting the shut-off aspirator of a service station fuelnozzle. FIG. 16 shows the running (cap-on) condition of the system: FIG.17 shows the cap-off condition; and FIG. 18 shows the refuelingcondition. FIGS. 21, 22, and 23 are expanded views of the upper portionof the filler pipe of FIGS. 16, 17, and 18, respectively.

FIG. 19 shows a single dome fuel tank wherein the conduit whichestablishes the fill line comprises the space between two hoses whichconnect the filler pipe assembly to the fuel tank.

FIG. 20 shows the cap-on condition of a fuel tank having multiple domesand a separate conduit for establishing the fill line.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference now to the drawings, wherein like reference charactersdesignate like or corresponding parts throughout the several views,there is shown in FIGS. 1 and 2 a perspective and an exploded view,respectively, of fuel filler pipe assembly 10 constructed in accordancewith the present invention.

Assembly 10 includes outer tube 12 which is attached to outer hose 14 byhose clamp 16. Outer hose 14, in turn, is attached to the vehicle's fueltank (not shown) by, for example, a further hose clamp (not shown). Atits upper end, outer tube 12 forms mouth 18 for receiving fuel. Theinside surface of mouth 18 includes female screw thread 20 which mateswith male screw thread 22 carried by cap 24. Flange 26 is attached toouter tube 12 in the region of mouth 18 and is used to mount assembly 10to the vehicle by means of, for example, sheet metal screws which passthrough screw holes 28.

Within outer tube 12 is located inner tube 30 which is attached to innerhose 36 by hose clamp 38. Inner hose 36 lies within outer hose 14.Depending on the desired level to which the vehicle's fuel tank is to befilled, inner hose 36 will either extend beyond outer outer hose 14 intothe vehicle's fuel tank or will end within the outer hose. In eithercase, inner hose 36 is not clamped to the fuel tank, but simply rideswithin the outer hose. For some tank configurations, inner hose 36 canbe eliminated.

The upper end of inner tube 30 is sealed to the inner surface of outertube 12 by means of flange 32 and grommet 34. During filling of thevehicle's fuel tank, grommet 34 forms a seal around the fuel fillernozzle so as to prevent substantial amounts of fuel vapors form passingout of the fuel tank by means of inner tube 30. Inner tube 30 includesslit 106 which provides a passageway for fuel to move from conduit 42 toconduit 40 as the fuel tank becomes full (see FIG. 12.) The presence offuel in conduit 40 serves to trigger the automatic shut off sensor(aspirator) used on conventional fuel pump nozzles to shut off the fuelpump when the fuel tank is full. Inner tube 30 also includes aperture100 which provides a vent path for fuel vapors within conduit 40 whichare displaced by the incoming fuel, that is, aperture 100 vents conduit40 so that slit 106 does not become vapor locked.

Outer tube 12 and inner tube 30 are preferably made of a plasticmaterial, such as, for example, nylon, acetal or polyester, and can befastened to each other by, for example, ultrasonic welding. Grommet 34is preferably made of a fluoroelastomer.

Inner tube 30 functions as a partition and divides the interior of outertube 12 into conduits 40 and 42. Conduit 40 extends from mouth 18towards the fuel tank and serves to carry fuel from the mouth into thetank. Conduit 42 extends away from the fuel tank, is isolated from mouth18, and serves to carry fuel vapors out of the fuel tank.

As can be seen most clearly in FIGS. 1-2, the upper portion of assembly10 includes housing 46 and cover plate 48 which are attached together byscrews 50 which pass through screw holes 52 in the cover plate and arereceived in screw holes 54 in the housing. Alternatively and preferably,the housing and outer tube 12 are molded as a single unit out of aplastic material, such as those discussed above, the cover plate is alsomade of plastic, and the housing and the cover plate are attachedtogether by ultrasonic welding.

As shown in FIG. 1, hose 56 is attached to housing 46 at port 58 bymeans of hose clamp 60. Hose 56 leads to a vapor capture device (notshown), such as, a charcoal canister, which is mounted on the vehicle ata suitable location.

Housing 46 and cover plate 48 together form conduit 44 (see FIGS. 5-7)for connecting conduit 42 to the vapor capture device. Housing 46 andcover plate 48 also contain and form part of valve assembly 13 wherebyconduit 44 is opened and closed in coordination with the detachment andattachment of cap 24 to mouth 18.

Valve assembly 13 includes: normally-closed valve 62; upper cam arm 64;lower cam arm 72; cylindrical post 66, which is journaled in cylindricalhousing 68 formed in housing 46 and a corresponding cylindrical housingformed in cover 48 (not shown): 0-ring 70, which is received on post 66and forms a seal between the post and the wall of the cylindricalhousing so as to create a vapor barrier between the upper and lower camarms; and spring 74, which urges lower cam arm 72 into contact withvalve 62 so as to move the valve into its open position. Cylindricalpost 66 connects lower cam arm 72 to upper cam arm 64 so that rotationof the upper cam arm results in corresponding rotation of the lower camarm.

As can be seen most clearly in FIG. 7, valve 62 includes piston 76,spring 78, and 0-ring 80 which mates with surface 82 of housing 46 toclose the valve. Spring 78 is preferably chosen so that valve 62 willautomatically open at a predetermined pressure, e.g., a pressure on theorder of 1-2 psi, so as to relieve excess pressure within the fuel tanksuch as can occur under hot environmental conditions.

The coordination between the opening and closing of valve 62 and therotation of male thread 22 in female thread 20 is illustrated in FIGS.8-11, where FIGS. 8 and 10 show the positions of upper cam arm 64, lowercam arm 72, spring 74, and valve 62 when the male thread is inengagement with upper cam arm 64, and FIGS. 9 and 11 show the positionsof the same components when the male thread is out of engagement withthe upper cam arm.

As shown in these figures, engagement causes lower arm 72 to rotatecounterclockwise against the force of spring 74 thus allowing valve 62to move into its normally closed position, while disengagement allowsspring 74 to move lower arm 72 into contact with valve piston 76 so asto open the valve by disengaging 0-ring 80 from surface 82. As shown inFIG. 6, upper arm 64 is preferably located towards the bottom of femalescrew thread 20 so that valve 62 opens at the beginning of the processof removing cap 24 from mouth 18. In particular, valve 62 opens beforeseal 25 carried by cap 24 disengages from mouth 18 of the assembly (seeFIG. 5). In this way, any residual pressure which may be in the fueltank is vented into the vapor capture device prior to removal of thecap, thus preventing the escape of fuel vapors into the atmosphere.

In addition to valve 62, assembly 10 also includes valve 84 which closesconduit 42 as liquid fuel reaches a predetermined height in thatconduit. As shown in FIG. 6, ball 86 which seats in seal 88 can be usedfor this purpose. As shown in FIG. 12, assembly 10 is mounted on thevehicle so that ball 86 moves essentially vertically, i.e., the assemblyis mounted so that housing 90 for ball 86 is oriented vertically. Ball86, which must have a lower density than the fuel used in the vehicle,can be a hollow ball made out of polypropylene. Seal 88 includesflexible lip 89 which, along with the vertical movement of the ball,helps prevent the ball from hanging up on the seal.

FIGS. 13-15 illustrate the use of baffle assembly 92 for controllingsplashing of liquid fuel onto ball 86. Because of the pumping ratesused, the filling of a vehicle fuel tank by means of a conventionalservice station fuel pump results in substantial splashing of the liquidfuel within the fuel tank. This splashing can cause ball 86 to moveupward in housing 90 and seat in seal 88 before the fuel tank has beencompletely filled. This seating, in turn, causes back pressure inconduits 40 and 42 which shuts off the service station fuel pump.

Moreover, if a grommet 34 has been used which forms a seal with the fuelpump's nozzle, as is preferred, ball 86 will remain seated in seal 88even after the fuel pump has shut itself off, due to the internalpressure within the fuel tank produced by 1) the action of the fuel pumpprior to shut off, and 2) the vapor pressure of the fuel in the fueltank. Although this internal pressure will eventually bleed off throughleakage around grommet 34, as a practical matter, to resume pumping in areasonable amount of time, the user will need to remove the fuel pumpnozzle from the filler pipe assembly in order to vent the internalpressure. Baffle assembly 92, by blocking the passage of splashed fuelto ball 86, minimizes the chances that such premature seating of ball 86in seal 88 will occur before the fuel tank has been fully filled.

As shown in FIGS. 13-15, baffle assembly 92 can consist of a series offour transverse baffles 94 and a midline baffle 98. These baffles createthe circuitous route illustrated by arrows 96 in FIG. 14 which fuel mustfollow to reach ball 86. In practice, it has been found thatsubstantially no fuel splashes are large enough or have sufficientenergy to traverse the full circuit and then move ball 86 up into seal88 without first having entered slot 106 and contacted the aspirator onthe nozzle of the service station fuel pump, thus shutting off thatpump. Baffle assembly 92 also includes drain passages 102 and 104 whichrapidly drain splashed fuel back into the tank so as to minimize thechance that multiple splashes will combine with one another to move theball. Other baffle constructions besides the one illustrated in thefigures can be used in the practice of the invention. For example, sixbaffles, rather than four baffles, can be used to provide even greatersplash protection for ball 86.

As shown in the figures, baffle assembly 92 is conveniently formed onthe outside surface of inner tube 30. In addition to the baffleassembly, guide members 108, 110 and 112, which control the movement ofball 86, are also formed on this surface. As shown in FIG. 14, valve 84preferably includes a second ball 115. This ball is denser than theliquid fuel and thus remains in contact with top baffle 94 during normaloperation of the vehicle. As such, it serves as an additional obstaclefor splashed fuel. If a vehicle should roll over during accident, ball115 serves the important function of forcing ball 86 into seal 88 thuspreventing fuel from draining out of the fuel tank through conduits 42and 44. Ball 115 can be made of, for example, stainless steel.

As also shown in FIG. 14, filler pipe assembly 10 preferably includesrelief valve 114. This normally-closed valve is designed to open whenthe pressure in conduit 42 exceeds a predetermined value, such as 1-2psi. Under normal conditions, this valve remains shut during filling ofthe fuel tank. However, if valve 84 should close during filling and iffuel should continue to be pumped into the tank, valve 114 will openallowing the excess fuel to pass out of conduit 42 and into mouth 18,thus relieving excess tank pressure and alerting the operator that theservice station fuel pump has malfunctioned.

Inner tube 30 and its associated baffle assembly 92 can be attached toouter tube 12 by means of screws (not shown) and screw holes 116.Alternatively, the two tubes can be bonded together by, for example,ultrasonic welding. Grommet 34 forms a seal between the upper end ofinner tube 30 and the body of outer tube 12. Grommet 34 also forms aseal about the fuel pump nozzle when the nozzle is inserted into conduit40. As shown in FIG. 14, inner tube 30 is offset from the center line ofouter tube 12. This permits the spring used on some fuel pump nozzles toengage threads 20 in mouth 18 of the filler pipe assembly. As furthershown in FIG. 14, sea 88 can be held in place by retaining ring 118.

Based on the foregoing, the operation of the fuel filler pipe assemblyof the present invention is as follows. When cap 24 is in place on outertube 12, the assembly seals the vehicle's fuel tank by means ofnormally-closed valve 62 and seal 25 carried by the cap. Should excesspressure develop in the tank, valve 62 opens to vent the excess pressureinto the vapor capture device through conduits 42 and 44 and hose 56.

When cap 24 is removed from outer tube 12, valve 62 automatically opensso that the fuel vapors within the tank are vented to the vapor capturedevice. During filling of the tank with fuel, valve 62 remains open sothat the vapors displaced by the incoming fuel pass through the valveinto the vapor capture device. As the tank becomes full, liquid fuelrises in conduit 42 causing ball 86 to seat in seal 88. This preventssubstantial quantities of liquid fuel from flowing through conduits 42and 44 into the vapor capture device. When cap 24 is replaced on outertube 12, valve 62 closes and the fuel tank is once again sealed.

With reference now to FIGS. 16-23, these figures illustrate theapplication of the present invention to the problem of expulsion of fuelfrom a vehicle fuel tank. As shown in FIG. 16, the expulsion controlsystem includes valve assembly 13 whose operation is controlled by theattachment and detachment of cap 24 to mouth 18. Valve assembly 13, cap24 and mouth 18 are constructed and operate in the manner describedabove. For purposes of clarity in describing the vapor flow pathsthrough the system, the details of construction of assembly 13, as wellas the details of construction of baffle assembly 92, are not shown inFIGS. 16-23.

As shown in FIG. 16, fuel tank 201 has a single dome 241 which forms theuppermost portion of the fuel tank. Conduits 231 and 233 connect thefuel tank to main fuel-carrying conduit 232. Conduit 231 defines thefill line for the tank. This conduit is attached to conduit 232 belowthe level of flapper door 220. During fill-up, this conduit carriesliquid fuel to the fuel pump nozzle's aspirator when the level of fuelin the tank rises above the top of the conduit. Conduit 233 carries fuelvapors from tank 201 to valve assembly 13. This conduit joins withconduit 232 between flapper door 210 and flapper door 220, i.e., at thelevel of cap-controlled valve assembly 13.

Flapper door 210 is spring loaded against seal 211. As shown in FIGS. 18and 23, this seal also engages and forms a seal with fuel pump nozzle202 when the nozzle is inserted in conduit 232 during tank fill-up. Theend of conduit 233 carries seal 209. When flapper door 210 is pushedopen by fuel nozzle 202, the door's back or lower side engages seal 209and thus closes conduit 233. Flapper door 210 thus performs two sealingoperations: one with seal 211 when the door is in its normally-closedposition and one with seal 209 when the door is in its open position.

Flapper door 220 is spring loaded against seal 221. Unlike seal 211,seal 221 does not form a seal with fuel nozzle 202 when the nozzle isinserted in conduit 232. In this way, as the tank is filled, fuel vaporscan pass around the nozzle, through flapper door 220, through valveassembly 13, and out conduit 44 to a vapor capture device (not shown).

FIGS. 16 and 21 show the configuration of the expulsion control systemduring normal operation of the vehicle, e.g., when the vehicle isrunning. Vapors evaporating from the fuel in the tank exit from dome 241through conduit 233, past baffle assembly 92, past ball 86, until theyreach normally-closed, spring-operated valve 62. This valve is designedto open at a predetermined pressure, e.g., 1-2 psi. Accordingly, thevalve stays closed until the pressure in dome 241 exceeds thepredetermined pressure. The valve then opens allowing fuel vapors topass into conduit 44 and thence to the vapor capture device. Liquid fueldoes not contact ball 86 in this configuration because flapper door 220is sealed against seal 221 and because conduit 233, which is neversubmerged during normal operation, vents the pressure in the tank to alow value, e.g., on the order of 1-2 psi, through valve 62.

FIGS. 17 and 22 show the configuration of the system with cap 24removed. As shown in, for example, FIG. 11, with the cap removed, spring74 is free to move lever arm 72 against valve body 76 to open valve 62.Fuel vapors now flow out of dome 241, through conduit 233, past baffleassembly 92, past ball 86, through valve 62 and out of conduit 44 to thevapor capture device. These flows continue until the tank pressure dropsto atmospheric pressure.

Even if the liquid fuel should boil during this process, no expulsionwill occur because flapper door 210 is sealed against seal 211. Also,flapper door 220 is sealed against seal 221 thus providing additionalprotection against expulsion. The seal between flapper door 200 and seal221 also prevents liquid fuel from reaching ball 86. This is animportant function for this flapper door since such liquid fuel coulddrive ball 86 into seal 88 and thus seal shut the vent path before allof the pressure in the tank had been vented.

FIGS. 18 and 23 show the configuration of the system during fill-up.Fuel pump nozzle 202 is inserted through seals 211 and 221, and opensdoors 210 and 220. As discussed above, seal 211 is sized to form a sealwith the outer surface of the nozzle. This seal prevents vapor andliquid fuel from escaping from mouth 18 if any residual pressure shouldremain in tank 201. As also discussed above, a seal is not formedbetween the nozzle and seal 221. The opening of door 210 by nozzle 202moves the door into sealing contact with seal 209, thus closing offconduit 233. The closing of this conduit prevents venting of dome 241and thus results in normal nozzle shut-off when conduit 231 becomescovered with fuel.

As the fill-up procedes, vapor moves up passages 231 and 232, throughbaffle assembly 92, past ball 86, through open valve 62, and throughconduit 44 to the vapor capture device. As discussed above, during thisprocess, baffle assembly 92 controls the splashing of liquid fuel ontoball 86, and ball 86 prevents substantial amounts of liquid fuel frombeing pumped through the cap-controlled valve assembly into the vaporcapture device as the tank becomes completely full.

After fill-up has been completed, nozzle 202 is removed from conduit232, ad the system returns to the configuration of FIGS. 17 and 22. Cap24 is then replaced, bringing the system to the normal operatingconfiguration of FIGS. 16 and 21. The vehicle is then ready for useuntil the next refueling becomes necessary.

FIGS. 19 and 20 illustrate the application of the expulsion controlsystem to fuel tanks having configurations different from that shown inFIGS. 16-18. In particular, in FIG. 19, conduit 231 is not formed as aseparate tube, but rather comprises the space between outer hose 14 andinner hose 36. In FIG. 20, fuel tank 203 has two domes 204 and 205,instead of a single dome 241. For this configuration, conduit 233 isattached to each of the domes. Also, for this tank, conduit 231 runs tothe space between the domes, rather than to a point just above conduit232.

FIGS. 19 and 20 show the expulsion control system in its normaloperating (cap-on) configuration. The cap-off and refuelingconfigurations are the same as those shown in FIGS. 17 and 18 (and FIGS.22 and 23) with the alternate tank constructions substituted for thetank construction of FIGS. 17 and 18. The operation of the expulsioncontrol system for each of the cap-on, cap-off, and refueling conditionsis the same for the tank configurations of FIGS. 19 and 20 as thatdescribed above for the tank configuration of FIGS. 16-18 and 21-23. Aswill be evident, based on the disclosure herein, the expulsion controlsystem of the present invention can be readily adapted to tankconfigurations other than those shown by persons of ordinary skill inthe art.

The components of the fuel filler pipe assembly of the present inventioncan be made of standard materials used in the automotive industry. Forexample, as discussed above, outer tube 12, inner tube 30, housing 46,and cover plate 48 can be made of nylon, acetal or polyester. Valvepiston 76 can also be made out of these materials. 0-rings 70 and 80, aswell as grommet 34 and seals 88, 209, 211 and 221, can be made of afluoroelastomer, while post 66, cam arms 64 and 72, and flapper doors210 and 220 can be made of metal or high strength thermoplasticmaterials. Other suitable materials for the components making up thefiller pipe assembly will be evident to persons skilled in the art inview of the present disclosure.

Although specific embodiments of the invention have been described andillustrated, it is to be understood that modifications can be madewithout departing from the invention's spirit and scope. For example,partitions other than inner tube 30 can be used to form two conduitswithin outer tube 12. Similarly, the components of the invention can bearranged relative to one another in a variety of configurations otherthan those shown.

What is claimed is:
 1. A method for venting a dome of a vehicle fuel tank, said tank having a filler pipe which (i) receives a fuel pump nozzle during filling of the tank and (ii) is sealed by a removable cap, said method comprising the steps:(a) providing a vent path leading from the dome to a vapor capture device; (b) when the cap is in place, opening the vent path when the pressure in the dome rises above a threshold value and closing the vent path when the pressure in the dome drops below the threshold value; (c) when the cap is removed and a fuel nozzle is not inserted in the filler pipe, opening the vent path irrespective of the pressure in the dome: and (d) when the cap is removed and a fuel nozzle is inserted in the filler pipe, closing the vent path irrespective of the pressure in the dome. 